I got my chickens (fully grown) about two weeks ago. They are generally very docile and gentle. However, they have been a bit aggressive lately (the past 2-3 days)... When I am refilling their food, they peck my arms and try to jump anywhere to reach the bag of food. I even had to slightly push one of them away because she was pecking me quite hard. Does this have a reason? Or is this just them getting very comfortable around me?